Figure 1. Conjunctival erythema without discharge. Source: James H. Brien, DO.
He is sent for admission. Intake lab results show the following:

Figure 2. Generalized polymorphic eruption. Source: James H. Brien, DO.
What is your diagnosis ?
A. Kawasaki disease
B. Multisystem inflammatory syndrome in children
C.Rubeola
D. Streptococcal scarlet fever
Answer and discussion:
With 1 more day of fever, this child would meet the diagnostic criteria for Kawasaki disease, or KD (choice A), which consists of 5 days of fever, bulbar conjunctivitis with limbal sparing, polymorphic rash, changes in extremities (swelling and/or erythema), non-suppurative cervical lymphadenitis and inflammation of the mucous membranes of the mouth and lips. Some will also count inflammation of the urethra or vagina or the perianal mucosal junction. Many experts suggest making the diagnosis before the 5th day of fever to avoid a delay in treatment if the criteria are there without further explanation. Also, even if there is evidence of a viral URI, as in this patient, this should not rule out the diagnosis of KD as it can occur concurrently. However, if the conjunctivitis is purulent and/or the erythema of the throat is suppurative, the diagnosis of KD should not be made using these criteria as they would not be compatible with KD but would more likely indicate a adenovirus. It would be extremely unlikely for KD and adenovirus infection to occur in the same patient at the same time. To avoid missing a case of KD, criteria have been established for those who lack sufficient criteria. AAPs red book has a detailed table to aid in the evaluation of a suspected incomplete KD (page 459), which can also be found here.
The treatment of KD is based on immunoglobulin IV (IVIg) at a rate of 2 g/kg. More than one dose may be needed. High-dose aspirin (80 to 100 mg/kg per day divided into four doses) is used until apyrexia for 48 to 72 hours, followed by low-dose aspirin (3 to 5 mg/kg per day ). This is usually stopped by the cardiologist during follow-up. Repeated administration of IVIG or other anti-inflammatory agents, such as infliximab or cyclosporine, should be done on the advice of a KD expert. As the patient progresses from the acute phase to the subacute phase of convalescence, he usually presents with significant thrombocytosis and scaling of the terminal digits and areas where the rash was most intense.
The similarities between KD and multisystem inflammatory syndrome in children (MIS-C) associated with COVID-19 are discussed in detail by Lee and colleagues in Borders in Pediatrics.
Rubella – also known as measles or first disease – presents as an acute febrile illness caused by the measles virus, characterized by progressive fever, with cough, coryza and conjunctivitis (the “three Cs”), as well as Koplik spots in the early days, and a morbilliform rash appearing on day 3 or 4. The rash usually first appears on the head and face, then spreads rapidly to the upper limbs and trunk (Figure 3 ), the confluence of the lesions creating patches of raised erythema. The diagnosis is usually confirmed by serological tests or viral detection by PCR of oral or respiratory secretions or blood. Physicians should be wary of false positives from both techniques if the patient has recently received MMR vaccination. Treatment is supportive and includes vitamin A supplementation (see red book for more details).

Picture 3. Measles morbilliform eruption. Source: James H. Brien, DO.
Scarlet fever is a classic group A streptococcal (GAS) infection with a diffuse erythematous rash with a thin papular, sandpaper-like rash with a “strawberry tongue”, without ocular inflammation. The focus of GAS infection can be anywhere, except usually in the posterior pharynx and tonsils.
References:
American Academy of Pediatrics. Infectious Diseases Committee. Red book. Report of the Infectious Diseases Committee. Academy of Pediatrics; 2021. https://redbook.solutions.aap.org/redbook.aspx. Accessed November 21, 2022.
Lee MS, et al. front pediatrician. 2021; doi: 10.3389/fped.2021.640118.
For more information:
Brien is a member of the Healio Pediatrics Peer Perspective Board and Assistant Professor of Pediatric Infectious Diseases at McLane Children’s Hospital, Baylor Scott & White Health, in Temple, Texas. He can be contacted at jhbrien@aol.com.
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